Various disk cartridges to enclose a disklike data storage medium have been proposed so far.
For example, Japanese Patent Application Laid-Open Publication No. 9-153264 discloses a disk cartridge in which a disklike storage medium with one or two data storage sides (which will be simply referred to herein as a “disk”) is fully enclosed in a disk storage portion that is provided inside of a supporting base member consisting of upper and lower housings. The supporting base member has a chucking hole for allowing the turntable of a spindle motor and a damper to chuck a given disk and a head access window for allowing a head to read and write data from/on the disk. The chucking hole and the head access window are continuous with each other, and therefore, dust easily enters the cartridge or a finger mark is often left on the disk through these openings while this cartridge is carried. That is why a shutter that covers these openings is provided for the disk cartridge.
To get the disk chucked or to allow the optical head to access the entire data storage side of the disk, those openings need to be cover the range from around the center of the cartridge through an edge thereof. Also, in a disk cartridge with such a structure, the shutter is supposed to move linearly with respect to the cartridge case, and therefore, a space to store the shutter being opened is needed. For these reasons, the sizes of the openings depend on the outer dimensions of the cartridge. That is to say, it is difficult to design a small cartridge with big openings. As a result, in disk camcorders and other portable electronic devices that use a small cartridge, the maximum allowable size of the optical head is limited, which is a problem.
Also, in loading a disk drive with such a disk cartridge to read and write data from/on the disk enclosed in the cartridge, a space for allowing some error that should occur in positioning the disk cartridge in the disk drive needs to be left in the disk storage space between the upper and lower housings. As a result, the outer dimensions of the cartridge should increase for this reason, too. In addition, to allow such a positioning error, the disk needs to be movable in that space. In that case, however, the disk could move inconstantly within the disk cartridge to possibly get its data storage side scratched. Or the disk might collide against the inner wall of the disk cartridge to produce dust particles, which could deposit themselves on the disk, too.
Besides, the lower housing needs those openings for allowing the turntable of the spindle motor and the head to access the disk and the upper housing needs another opening for allowing the damper to access the disk. That is why a shutter to shut all of these openings at the same time should have a continuous C-shape that covers both the upper and lower housings. However, a shutter of such a shape is expensive, thus increasing the manufacturing cost of the disk cartridge. On top of that, a movement guide portion to open and close the C-shutter needs to be provided for either the upper housing or the lower housing so as to build a bridge across the head access window. And that guide portion limits the height of the head.
What is more, such a C-shutter should have a thin plate shape so as not to increase the thickness of the disk cartridge significantly. For that reason, such a thin shutter cannot guarantee sufficient mechanical strength. Therefore, if the disk cartridge were subjected to great impact, the shutter might be broken. Or if somebody stepped on the cartridge by mistake, the shutter could be deformed so much as to scratch the data storage side of the disk.